1. Field of the Invention
The present invention relates to an air conditioning controller which controls an air conditioner for a vehicle. More particularly, the present invention relates to an air conditioning controller for a hybrid car which has an electric motor in addition to an engine serving as a power source for motion of the vehicle.
2. Description of the Related Art
Usually, in air conditioners of vehicles, when an evaporator is sufficiently cooled and when the cooling load is low, use of a compressor is refrained in order to save energy.
In recent years, a hybrid car having an electric motor which generates driving force through electricity in combination with an engine which generates driving force through the combustion of fuel such as gasoline and the like has been proposed. Even when an engine is stopped, this hybrid car can travel by driving an electric motor with electric power supplied from batteries. Further, batteries may be charged beforehand, or batteries may be charged by electric power generated through the driving force from the engine while traveling.
Even in the aforementioned air conditioner in a hybrid car, a compressor must be driven whenever a vehicle interior portion is air-conditioned. For this reason, Japanese Patent Application Laid-Open (JP-A) No. 6-286459 discloses that when an engine has been stopped, it can be started again by operating the driving switch of an air conditioner so that a compressor is driven by the driving force of the engine.
Therefore, a motor for driving the compressor of an air conditioner is unnecessary. Further, it becomes possible to operate the air conditioner without making use of driving force generated from the electric motor or electric power generated from batteries for operating the electric motor.
In the hybrid car, when the vehicle stops, the engine stops. Accordingly, an engine can be prevented from being run unnecessarily in order to improve fuel economy.
However, while the engine stops, if the operating switch of an air conditioner is switched ON when the engine is off, the engine starts up. Moreover, if the vehicle stops traveling with the air conditioner in use, the engine keeps on running. As a result, wasteful consumption of fuel occurs.
In order to prevent such fuel wastage, a way of starting an engine in concert with the driving of a compressor has been thought of. However, an engine that keeps on starting up when a vehicle stops could annoy passengers.